1. Technical Field
The present invention relates to a cooling and dust collecting apparatus of a machine tool for cooling a cutter and discharging cutting chips.
2. Related Art
There have been proposed various types of cooling and dust collecting apparatuses for machine tools. For example, Japanese Patent Laid-Open Publication No. Toku-Kai-Sho 58-59746 discloses a cooling and dust collecting apparatus for a machine tool in which a drill is surrounded by a hood and the drill is cooled by spraying a mist of a cutting oil towards the center of the drill in several directions.
Further, Japanese Patent Laid- Open Publication Nos. Toku-Kai-Sho 63-300807 and Toku-Kai-Hei 3-3713 disclose a pressure foot for printed circuit board drilling machines. The pressure foot is connected to a cutting chip sucking device through a hose so as to keep the inside of the pressure foot in the negative pressure state. Additionally, compressed air is horizontally blown from the vicinity of the front end of the pressure foot in the tangent direction of the drill. The compressed air expands in the pressure foot almost in an adiabatic state, thereby the temperature there-in sharply lowering. The compressed air thus cooled down cools the drill of the drilling machine and is discharged to the cutting chip sucking device together with cutting chips.
However, in the abovementioned cooling and dust collecting apparatuses for machine tools, since cutting oil mist or compressed air is blown to a cutter in nearly horizontal direction, a portion of the cutter exposed out of a workpiece is cooled, whereas portion hidden therein is not cooled. In addition, cutting chips which are caught in a hole or groove are not discharged.
The applicant of the present invention has disclosed a cooling and dust collecting apparatus for machine tools in Japan Patent Laid-Open Publication No. Toku-Gan-Hei 4-210464 so as to solve the problems as described above. The cooling and dust collecting apparatus disclosed therein comprises a cooling and dust collecting housing installed at the lower end of the spindle housing in such a way as enclosing a main shaft and a cutter of the machine tool, a plurality of cold air passages which are built in the cooling and dust collecting housing and communicate a cold air intake portion connected to an external compressed cold air supplying device with a first and second cold air outlet portions, a cutting chip discharging passage which is built in the cooling and dust collecting housing and communicates a discharge port connected to an external cutting chip sucking device with an internal space of the cooling and dust collecting housing, an elastic hood having slits at the foot thereof and suspended from the bottom edge of the cooling and dust collecting housing. The first cold air outlet portion injects the compressed cold air towards the shaft of the cutter and the second cold air outlet portion injects the compressed cold air in the diagonally downward direction and in the tangent direction of the outer periphery of the cutter edge so as to detach cutting chips from the cutter or to float cutting chips away from holes and grooves. These cutting chips are sucked and discharged outside by the external cutting chip sucking device. The elastic food acts as preventing the compressed cold air injected to the cutter and cutting chips from flowing out of the cooling and dust collecting housing.
However, in the cooling and dust collecting apparatus for a machine tool according to the patent No. Toku-Gan-Hei 4-210464, there is the defect that the discharging of cutting chips and the cooling of the cutter can not be performed satisfactorily depending upon the cutting conditions, since the flow-out of the compressed cold air and the cutting chips is prevented only by the elastic hood.